88 THE BEGINNINGS OF LIFE. 



leading part in organic actions. According to Mulder, 

 the formula of albumen is 10 (C 40 H 31 N 5 O 12 ) -f- S 2 P. 

 That is to say, with the sulphur and phosphorus there 

 are united ten equivalents of a compound atom con- 

 taining forty atoms of carbon, thirty-one of hydrogen, 

 five of nitrogen, and twelve of oxygen : the atom 

 being thus made up of nearly nine hundred ultimate 

 atoms.' 



These complex nitrogenous compounds, to the pro- 

 perties of which we have just been alluding, belong to 

 the class of bodies named colloids by Professor Graham. 

 They all have an extremely low diffusive power when 

 in solution, and on this account they have been sepa- 

 rated from the crystalloids^ or kinds of matter which 

 tend to crystallize, and also undergo diffusion much 

 more rapidly. Gelatine may be taken as the type of 

 this colloidal condition of matter. A most radical dis- 

 tinction is presumed to exist between crystalloids and 

 colloids, in regard to their intimate molecular con- 

 stitution. Professor Graham says 1 : 'Every physical 

 and chemical property is characteristically modified in 

 each class. They appear like different worlds of matter, 

 and give occasion to a corresponding division of chemical 

 science. The distinction between these kinds of matter 

 is that subsisting between the material of a mineral, 

 and the material of an organized mass.' Referring to 

 the colloidal class of substances, Professor Graham also 



1 'Phil. Trans.' 1861, p. 220. 



